As in most businesses it is important for telecom operators to price differentiate services to their users in order to maximise profits. Parameters such as duration of telephone conversation, user class of service, distance, time of day of conversation and user service classes have been used in pricing models allowing for high a capacity utilisation. Recently, the advent of GPRS has made it possible to charge customers, according to the amount of data, which is transmitted to and from the mobile terminal in question, such that the user is not charged for downtime and interruptions.
Mobile pre-paid subscriptions, i.e. a subscription type involving a fixed credit limit often associated with the acquisition of a “pre-paid” SIM card, have recently shown strong growth. As opposed to traditional subscribers, which can be billed after the service is delivered, operators need the ability to terminate services to pre-paid customers in case the credit limit of a given user is reached. Since the service delivered to the user may involve many operators, possibly virtual operators, an exact and prompt measurement of service utilisation is therefore needed. Pre-paid services, has therefore necessitated an ability to charge in “real time”.
It is believed that new services such as MMS will be one important driver for the change to 3G networks. A consistent pricing model of such services is believed to be important for users to adopt them. Advantageously, the user should expect a fixed “low” price level for transmitting a MMS, such that the service is perceived as being equivalent to other competing services, such as sending a post card. It is noted that a picture of a given resolution may be of varying data size depending on the coding principle and the motive captured.
According to the 3'rd generation partnership project (3GPP) technical specification, 3G TS 23.060 a common packet domain Core Network is used for both GSM and UMTS. Such a system has been shown in FIG. 1. A similar system has been shown in WO99/05828.
The above Core Network provides packet-switched (PS) services and is designed to support several quality of service levels in order to allow efficient transfer of non real-time traffic (e.g., intermittent and bursty data transfers, occasional transmission of large volumes of data) and real-time traffic (e.g., voice, video). One class of quality of service pertains to a low throughput and a low delay; another class pertains to higher throughput and longer delay and a further class pertains to relatively long delays and high through-put.
Applications based on standard data protocols and SMS are supported, and interworking is defined with IP networks. Charging is rendered flexible and allows Internet Service Providers to bill according to the amount of data transferred, the QoS supported, and the duration of the connection.
Each PLMN has two access points, the radio interface (labelled Um in GSM and Uu in UMTS) used for mobile access and the R reference point used for origination or reception of messages.
An interface differs from a reference point in that an interface is defined where specific information is exchanged and needs to be fully recognised. There is an inter PLMN interface called Gp that connects two independent packet domain networks for message exchange. There is also a PLMN to fixed network (typically a packet data network) reference point called Gi.
There may be more than a single network interface to several different packet data (or other) networks. These networks may both differ in ownership as well as in communications protocol (e.g., TCP/IP etc.). The network operator should define and negotiate interconnect with each external (PDN or other) network.
Network interworking is required whenever a packet domain PLMN and any other network are involved in the execution of a service request. With reference to FIG. 1, interworking takes place through the Gi reference point and the Gp interface.
The internal mechanism for conveying the PDP (Packet Data Protocol) PDU (Packet Data Unit) through the PLMN is managed by the PLMN network operator and is not apparent to the data user. The use of the packet domain data service may have an impact on and increase the transfer time normally found for a message when communicated through a fixed packet data network.
The packet domain supports interworking with networks based on the Internet protocol (IP). The packet domain may provide compression of the TCP/IP header when an IP datagram is used within the context of a TCP connection.
The packet domain PLMN service is an IP domain, and mobile terminals offered service by a service provider may be globally addressable through the network operator's addressing scheme.
A GPRS Support Node (GSN) contains functionality required to support GPRS functionality for GSM and/or UMTS. In one PLMN, there may be more than one GSN.
The Gateway GPRS Support Node (GGSN) is the node that is accessed by the packet data network due to evaluation of the PDP address. It contains routing information for PS-attached users. The routing information is used to tunnel N-PDUs to the MS's current point of attachment, i.e., the Serving GPRS Support Node. The GGSN may request location information from the HLR via the optional Gc interface. The GGSN is the first point of PDN interconnection with a GSM PLMN supporting GPRS (i.e., the Gi reference point is supported by the GGSN). GGSN functionality is common for GSM and UMTS.
The Serving GPRS Support Node (SGSN) is the node that is serving the MS. The SGSN supports GPRS for GSM (i.e., the Gb interface is supported by the SGSN) and/or UMTS (i.e., the lu interface is supported by the SGSN).
In order to access the PS services, an MS shall first make its presence known to the network by performing a GPRS Attach. This makes the MS available for SMS over PS, paging via the SGSN, and notification of incoming PS data. According to the Attach, the IMSI (International Mobile Subscription Identity) of the mobile station (MS) is mapped to one or more packet data protocol addresses (PDP).
At PS Attach, the SGSN establishes a mobility management context containing information pertaining to e.g., mobility and security for the MS.
In order to send and receive PS data, the MS shall activate the Packet Data Protocol context that it wants to use. This operation makes the MS known in the corresponding GGSN, and interworking with external data networks can commence.
At PDP Context Activation, the SGSN establishes a PDP context, to be used for routing purposes, with the GGSN that the subscriber will be using.
According to the PDP context activation, a network bearer (IP) communication between the mobile station and for instance the Internet service provider (ISP) may be established. Moreover, a given class of Quality of Service is assigned for the communication to be performed.
The SGSN and GGSN functionalities may be combined in the same physical node, or they may reside in different physical nodes. SGSN and GGSN contain IP or other (operator's selection, e.g., ATM-SVC) routing functionality, and they may be interconnected with IP routers. In UMTS, the SGSN and RNC may be interconnected with one or more IP routers. When the SGSN and the GGSN are in different PLMNs, they are interconnected via the Gp interface. The Gp interface provides the functionality of the Gn interface, plus security functionality required for inter-PLMN communication. The security functionality is based on mutual agreements between operators.
The SGSN may send location information to the MSC/VLR via the optional Gs interface. The SGSN may receive paging requests from the MSC/VLR via the Gs interface.
The SMS-GMSCs and SMS-IWMSCs support SMS transmission via the SGSN. Optionally, the MSC/VLR can be enhanced for more-efficient co-ordination of packet-switched and circuit-switched services and functionality: e.g., combined GPRS and non-GPRS location updates.
User data is transferred transparently between the MS and the external data networks with a method known as encapsulation and tunnelling: data packets are equipped with PS-specific protocol information and transferred between the MS and the GGSN. This transparent transfer method lessens the requirement for the PLMN to interpret external data protocols, and it enables easy introduction of additional interworking protocols in the future.
An Application Server (AS) is connected to the Packet Data Network (PDN) for providing information. An Internet Service Provider (ISP), the PLMN, or an independent company may own the application server. The application server may offer MMS.
The packet domain logical architecture, as defined in 3GPP TS 23.060, defines the protocols involved in the various nodes. FIG. 2 shows the user plane protocol stacks, as defined in the 3GPP TS 23.060 for GSM. FIG. 3 shows the user plane protocol stacks, as defined in the 3GPP TS 23.060 for UMTS.
In both cases shown in FIGS. 2 and 3, the GTP-U protocol conveys both uplink and downlink payload between SGSN and GGSN nodes, the Gn (or Gp in a roaming situation) interface. FIGS. 2 and 3 shall not be explained further as their content is well known in the art.
Charging
In a mobile packet data network, real-time pre-paid charging may rely on the use of CAMEL as standardized in 3GPP TS 22.078, 23.078 and 29.078.
In FIG. 4, the charging performed in known GPRS networks have been further illustrated. As appears from the figure, the SGSN may belong to a first operator 1—which may be denoted as a visitor public land mobile network (VPLMN) and the GGSN may belong to a second operator 2—which may be denoted as a home public land mobile network (HPLMN). This node may for instance belong to operator 2.
Respective Charging Gateway Functionality (CGF) in individual nodes collects charging records from SGSNs and GGSNs. The HLR (Home Location Register) contains GSM and UMTS subscriber information. The HLR stores the IMSI (International Mobile Subscription Identity) and maps the IMSI to one or more packet data protocol addresses (PDP) and maps each PDP address to one GGSN.
The SGSN provides S-CDR (SGSN Charging Data Record) charging reports relating to transmitted traffic according to a PDP context to a CGF. The S-CDR reporting is not performed on a real time basis, and hence inapt for real time charging.
The GGSN also performs collection of charging information on the same traffic relating to a given PDP context, travelling through the GGSN by providing G-CDR (GGSN Charging Data Record) reports. The amount of traffic may be slightly different from the measurements performed in the SGSN. The G-CDR reporting is not performed on a real time basis.
As indicated in FIG. 4, a CAMEL SCP (Service Control Point) node collects charging reports over the Ge interface using the Camel Application Part (CAP) protocol. The CAMEL standard caters for reporting transferred payload volume as a single measurement, uplink and downlink together. The CAMEL interaction (Ge interface) reports the appropriate PDP context resource utilization to a pre-paid system (CAMEL GSM-SCF). The SGSN however lacks the ability to discriminate different kinds of payload flowing through the PDP context.
The prime basis for charging in a mobile packet data network (GPRS in GSM and UMTS networks) is anticipated—and indicated by operators—to be the amount of transmitted payload in a PDP context. According to 3GPP TS 32.200, it is the “Usage of the radio interface” that is to be measured, i.e. measurements are performed on the SNDCP layer (Gb interface) for GSM and on the GTP-U layer (lu interface) for UMTS.
Services may be charged for separately, but still provided through the same PDP context. The payload required to provide the service should not (normally) be accounted for with respect to amount of payload to charge.
A known Packet Inspection and Service Classification (PISC) system interacting with a GGSN node has been provided and sold by Ericsson under the name “Flexible Bearer Charging (FBC) system”. Currently, such systems are dealt with under the designation Traffic Plane Function (TPF) in 3GPP TR 23.825. The PICS system performs packet inspections for given PDP contexts and assesses the given class of service used for the given PDP context. Based on the inspection, the FBC functionality provides reports of the volume of traffic for the given class of services provided. The FBC may provide volume and class for each PDP packet sent or received in a given PDP context.
The GGSN lacks a standardized real time charging interface towards a pre-paid system. The GGSN moreover lacks a control mechanism to be used for shutting down a PDP context, when the user account is empty.
FIGS. 5, 6 and 7 show various known GTP header formats as defined in 3GPP TS 29.060.